Projections and protuberances ; strange scaly serpentine structures ....
John McGrath attempts to make sense of a bewildering array of horns , spines , tentacles and nasal extensions .
Facial appendages , in the form of ‘ horns ’, ‘ eyelashes ’ and other similar structures , are surprisingly common amongst snakes , and have evolved independently in a number of lineages . But what is the purpose of these bizarre accessories ; what advantages do they confer and what were the selective pressures driving their acquisition ?
Nasal horns and eyelashes are particularly prevalent amongst the Viperidae , a family of venomous snakes that is widespread across every continent excepting Australia and the polar regions . Viperids are characterised by a stocky body and short tail , keeled scales and a triangular-shaped head armed with long , hinged fangs . They are typically nocturnal ambush hunters that employ a ‘ strike and release ’ technique , and must therefore track prey items until they inevitably succumb to the hemotoxic venom . Intriguingly , the ability to locate envenomated prey is enhanced by proteins contained in the venom . Most species of viperids are ovoviviparous , a trait which is obviously beneficial in temperate climates such as those of Canada , South America and Great Britain .
The Gaboon Viper ( Bitis gabonica ) may grow up to 2m in length and is quite possibly the world ’ s heaviest venomous snake . Hailing from the rainforests and savannah of sub- Saharan Africa , it is also notable for having the longest fangs ( up to 5cm ) and the largest venom yield of any living species of snake . In fact , significant sexual dimorphism exists in the length of fangs , with those of males being considerably longer than females . But Gaboon Vipers also possess a pair of distinctive , horn-like projections located between their nostrils . The Rhinoceros Viper ( B . nasicornis ), from Central and West Africa , has two or three prominent horn-like nasal scales , while Lataste ’ s Viper ( Vipera latastei ); from southern Europe and northern Africa , has a single horn , as does the Long-nosed Viper ( V . ammodytes ) from southern
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